Acoustic radiation force impulse elastography of the kidneys: is shear wave velocity affected by tissue fibrosis or renal blood flow?

The association between renal medullary and cortical fibrosis, stiffness, and concentrating capacity: an observational, single-center cross-sectional study

BACKGROUND

Fibrosis is a common final pathway leading to end-stage renal failure. As the renal medulla and cortex contain different nephron segments, we analyzed the factors associated with the progression of renal medullary and cortical fibrosis.

METHODS

A total of 120 patients who underwent renal biopsy at Kawashima Hospital between May 2019 and October 2022 were enrolled in this retrospective study. Renal medullary and cortical fibrosis and stiffness were evaluated using Masson's trichrome staining and shear wave elastography, respectively. Maximum urine osmolality in the Fishberg concentration test was also examined.

RESULTS

Medullary fibrosis was positively correlated with cortical fibrosis (p < 0.0001) and log-converted urinary β2-microglobulin (MG) (log urinary β2-MG) (p = 0.022) and negatively correlated with estimated glomerular filtration rate (eGFR) (p = 0.0002). Cortical fibrosis also correlated with log urinary β2-MG, eGFR, and maximum urine osmolality. Multivariate analysis revealed that cortical fibrosis levels (odds ratio [OR]: 1.063) and medullary stiffness (OR: 1.089) were significantly associated with medullar fibrosis (≧45%). The severe fibrosis group with both medullary fibrosis (≧45%) and cortical fibrosis (≧25%) had lower eGFR and maximum urine osmolality values and higher urinary β2-MG levels than the other groups.

CONCLUSIONS

Patients with disorders involving both renal medullary and cortical fibrosis had decreased maximum urine osmolality but had no abnormalities in the urinary concentrating capacities with either condition. Renal medullary and cortical fibrosis were positively correlated with urinary β2-MG, but not with urinary N-acetyl-beta-D-glucosaminidase.

In silico analysis reveals the prospects of renal anisotropy in improving chronic kidney disease detection using ultrasound shear wave elastography

Renal anisotropy is a complex property of the kidney and often poses a challenge in obtaining consistent measurements when using shear wave elastography to detect chronic kidney disease. To circumvent the challenge posed by renal anisotropy in clinical settings, a dimensionless biomarker termed the 'anisotropic ratio' was introduced to establish a correlation between changes in degree of renal anisotropy and progression of chronic kidney disease through an in silico perspective. To achieve this, an efficient model reduction approach was developed to model the anisotropic property of kidneys. Good agreement between the numerical and experimental data were obtained, as percentage errors of less than 5.5% were reported when compared against experimental phantom measurement from the literature. To demonstrate the applicability of the model to clinical measurements, the anisotropic ratio of sheep kidneys was quantified, with both numerical and derived experimental results reporting a value of .667. Analysis of the anisotropic ratio with progression of chronic kidney disease demonstrated that patients with normal kidneys would have a lower anisotropic ratio of .872 as opposed to patients suffering from renal impairment, in which the anisotropic ratio may increase to .904, as determined from this study. The findings demonstrate the potential of the anisotropic ratio in improving the detection of chronic kidney disease using shear wave elastography.

Prediction of acute rejection in renal allografts using shear-wave dispersion slope

OBJECTIVES

To evaluate the role of shear-wave dispersion slope for predicting renal allograft dysfunction.

METHODS

We retrospectively reviewed 128 kidney transplant recipients (median age, 55 years [interquartile range, 43-62 years]; male, 68) who underwent biopsy for allograft evaluation from November 2022 to February 2023. Cortex and renal sinus fat stiffness and shear-wave dispersion slope were obtained at shear-wave elastography (SWE). Cortex-to-sinus stiffness ratio (SR) and dispersion slope ratio (DSR)-related clinical and pathologic factors were evaluated using multivariable linear regression analysis. We conducted univariate and multivariate analyses for multiparametric ultrasound (US) parameters for identifying acute rejection and calculated the area under the receiver operating curve (AUC) values.

RESULTS

Of 128 patients, 31 (24.2%) demonstrated acute rejection. The SR value did not differ between patient groups (1.21 vs. 1.20, p = 0.47). Patients with acute rejection demonstrated a higher DSR than those without rejection (1.4 vs. 1.21, p < 0.01). Interstitial fibrosis and tubular atrophy grade (IFTA; coefficient, 0.11/grade; p = 0.04) and renal transplant and biopsy interval (coefficient, 0.00007/day; p = 0.03) were SR determinant factors, whereas only IFTA grade (coefficient, 0.10/grade; p = 0.01) for DSR. Multivariate analysis revealed mean resistive index (odds ratio [OR] 1.08, 95% confidence interval [CI] 1.02-1.14, p = 0.01) and DSR value (OR 16.0, 95% CI 3.0-85.8, p = 0.001) as independent factors for predicting acute rejection. An AUC of 0.74 for detecting acute rejection was achieved by combining the resistive index and DSR value.

CONCLUSION

Shear-wave dispersion slope obtained at SWE may help identify renal allograft dysfunction.

CLINICAL RELEVANCE STATEMENT

Acute rejection in renal allografts is a major cause of allograft failure, but noninvasive diagnosis is a challenge. Shear-wave dispersion slope can identify acute rejection non-invasively.

KEY POINTS

• The interstitial fibrosis and tubular atrophy grade was a determinant factor for stiffness ratio and shear-wave dispersion slope ratio between cortex and renal sinus fat. • Shear-wave dispersion slope ratio between cortex and renal sinus fat could identify acute rejection in renal allografts. • A shear-wave dispersion slope has a potential to reduce unnecessary renal biopsy for evaluating renal allografts.

Effect of proteinuria at relapse on shear wave velocity assessed using ultrasound elastography in children with idiopathic nephrotic syndrome

PURPOSE

Shear wave velocity (SWV) is an ultrasound elastography technique that provides much information for kidney disease assessment. However, the factors that alter SWV are not fully understood; it is unclear whether the variation in SWV seen in proteinuria associated with disease progression is due to tissue or proteinuria. This study investigated the effect of proteinuria on SWV.

METHODS

This prospective observational study compared SWV at remission with SWV at relapse in children treated for idiopathic nephrotic syndrome (INS) between April 2020 and December 2023. All relapses without oral steroids during the observation period were measured. SWV at remission was defined as the date closest to relapse during which repeated measurements were taken approximately every 3 months after steroid discontinuation.

RESULTS

Eight patients were treated for INS with a median observation period of 21.9 months (11.8-27.1). Of the 15 relapses, five that met the definition were considered for the study. The median interval between the measurement at relapse and remission was 40 days (11-55). SWV was significantly lower at relapse than remission (2.40 ± 0.20 m/s vs. 2.14 ± 0.15 m/s, P < 0.01).

CONCLUSIONS

SWV decreased in the presence of severe proteinuria at relapse compared to the remission measurements. Although more cases need to be studied, the decrease in SWV may reflect the mechanism by which protein leaks into the urine, not just a direct change caused by the presence of proteinuria.

Interpretable machine learning model integrating clinical and elastosonographic features to detect renal fibrosis in Asian patients with chronic kidney disease

BACKGROUND

Non-invasive renal fibrosis assessment is critical for tailoring personalized decision-making and managing follow-up in patients with chronic kidney disease (CKD). We aimed to exploit machine learning algorithms using clinical and elastosonographic features to distinguish moderate-severe fibrosis from mild fibrosis among CKD patients.

METHODS

A total of 162 patients with CKD who underwent shear wave elastography examinations and renal biopsies at our institution were prospectively enrolled. Four classifiers using machine learning algorithms, including eXtreme Gradient Boosting (XGBoost), Support Vector Machine (SVM), Light Gradient Boosting Machine (LightGBM), and K-Nearest Neighbor (KNN), which integrated elastosonographic features and clinical characteristics, were established to differentiate moderate-severe renal fibrosis from mild forms. The area under the receiver operating characteristic curve (AUC) and average precision were employed to compare the performance of constructed models, and the SHapley Additive exPlanations (SHAP) strategy was used to visualize and interpret the model output.

RESULTS

The XGBoost model outperformed the other developed machine learning models, demonstrating optimal diagnostic performance in both the primary (AUC = 0.97, 95% confidence level (CI) 0.94-0.99; average precision = 0.97, 95% CI 0.97-0.98) and five-fold cross-validation (AUC = 0.85, 95% CI 0.73-0.98; average precision = 0.90, 95% CI 0.86-0.93) datasets. The SHAP approach provided visual interpretation for XGBoost, highlighting the features' impact on the diagnostic process, wherein the estimated glomerular filtration rate provided the largest contribution to the model output, followed by the elastic modulus, then renal length, renal resistive index, and hypertension.

CONCLUSION

This study proposed an XGBoost model for distinguishing moderate-severe renal fibrosis from mild forms in CKD patients, which could be used to assist clinicians in decision-making and follow-up strategies. Moreover, the SHAP algorithm makes it feasible to visualize and interpret the feature processing and diagnostic processes of the model output.

Quantitative studies on B-mode ultrasound and point shear wave elastography of kidneys in nonazotemic dogs

Renal diseases in dogs can be diagnosed effectively using B-mode ultrasound. Point shear wave elastography (pSWE) has demonstrated usefulness in diagnosing renal diseases in human medicine. However, its application in veterinary medicine is in its nascent stage. It was hypothesized that establishing pSWE reference values in nonazotemic dogs would prove valuable in differentiating renal diseases. In light of this, a single-center, quantitative study with an objective to normalize B-mode ultrasound parameters and pSWE values of the kidney in nonazotemic dogs was conducted. A total of 198 animals presented with clinical signs of anorexia, vomiting, weight loss, and dehydration were enrolled in the study spanning 2 years. Among them, 52 nonazotemic dogs were included as subjects for the study. B-mode ultrasound quantitative parameters, including length (L), breadth (B), height (H), cortical thickness (RCT), and medulla thickness (RMT) of the kidneys, as well as the diameter of the aorta (Ao), were normalized. Additionally, calculated parameters such as L:Ao, B:Ao, H:Ao, RCT:Ao, and corticomedullary ratios were worked out. Point shear wave elastography values were obtained from the cranial and caudal poles of renal cortices using ElastPQ stiffness software. The pSWE values of kidneys in nonazotemic dogs were normalized. The mean ± standard error values were 1.04 ± 0.08 m/s (95% confidence interval: 0.88-1.19 m/s) and 4.18 ± 0.62 kPa (95% confidence interval: 2.93-5.42 kPa). In conclusion, B-mode ultrasound quantitative parameters, ratios, and pSWE values were normalized in nonazotemic dogs, which may prove valuable in differentiating renal pathologies in canine patients.

Seeing and Sensing the Hepatorenal Syndrome (HRS): The Growing Role of Ultrasound-Based Techniques as Non-Invasive Tools for the Diagnosis of HRS

More than half of patients hospitalized with liver cirrhosis are dealing with an episode of acute kidney injury; the most severe pattern is hepatorenal syndrome due to its negative prognosis. The main physiopathology mechanisms involve renal vasoconstriction and systemic inflammation. During the last decade, the definition of hepatorenal syndrome changed, but the validated criteria of diagnosis are still based on the serum creatinine level, which is a biomarker with multiple limitations. This is the reason why novel serum and urinary biomarkers have been intensively studied in recent years. Meanwhile, the imaging studies that use shear wave elastography are using renal stiffness as a surrogate for an early diagnosis. In this article, we focus on the physiopathology definition and highlight the novel tools used in the diagnosis of hepatorenal syndrome.

Analysis of the Efficacy of Elastography in Comparison with Dynamic Renal Nuclear Scintigraphy in the Evaluation of Unilateral Pelvi-Ureteric Junction Obstruction

INTRODUCTION

In hydronephrosis due to pelviureteric junction obstruction (PUJO), an obstruction to urine flow may lead to increased pelvic pressure, which may cause interstitial fibrosis and renal impairment. Recently, there have been reports on renal pelvic assessment using ultrasound elastography (USE). This study was conducted to see if USE can evaluate PUJO and if it can be correlated to the findings of the dynamic renal nuclear scan.

MATERIAL AND METHODS

In this observational study, only patients with unilateral PUJO underwent acoustic radiation force impulse (ARFI) elastography. A rectangular region of interest (ROI) measuring 5 × 10 mm was positioned on the cortex region of the upper, mid, and lower poles of the affected kidney. Three valid measurements were obtained, from which a mean value was calculated. A dynamic renal nuclear scan using Technetium-99m ethylene dicysteine (EC or TC99 m EC) was obtained and split renal function (SRF) was used for comparison.

RESULTS

In the group of 20 patients, the mean age was 3.37 years. The mean SRF of the affected kidney was 26.65 %, and the corresponding USE value was 0.45 kpa. The Spearman's rho correlation coefficient for SRF and USE was 1 and 0.672, respectively (p = 0.001). Elastography was not feasible if SRF was less than 20 %.

CONCLUSION

USE may be able to comment on the renal functional status of hydronephrosis. If USE is reported as non-feasible, it may suggest that renal function is grossly compromised. It may serve as an alternative diagnostic modality for renal functional evaluation.

LEVEL OF EVIDENCE

Level II, Prospective Cohort Study.

Association of renal elasticity evaluated by real-time shear wave elastography with renal fibrosis in patients with chronic kidney disease

OBJECTIVE

Renal fibrosis is a final common pathological hallmark in the progression of chronic kidney disease (CKD). Non-invasive evaluation of renal fibrosis by mapping renal stiffness obtained by shear wave elastography (SWE) may facilitate the clinical therapeutic regimen for CKD patients.

METHODS

A cohort of 162 patients diagnosed with CKD, who underwent renal biopsy, was prospectively and consecutively recruited between April 2019 and December 2021. The assessment of renal cortex stiffness was performed using SWE imaging. The patients were classified into different groups based on pathological renal fibrosis (mild group: n = 74; moderate-to-severe group: n = 88). Binary logistic regression model and generalized additive model were conducted to investigate the association of renal elasticity with renal fibrosis.

RESULTS

Compared with the mildly impaired group, the moderate-to-severe group showed a significant decline in renal elasticity (P < .001). In the fully adjusted model, each 10 kPa drop in renal elasticity was associated with a 3.5-fold increment in the risk of moderate-to-severe renal fibrosis (fully adjusted odds ratio, 4.54; 95% CI, 2.41-8.57). Particularly, participants in the lowest elasticity group (≤29.92 kPa) had a 20-fold increased chance of moderate-to-severe renal fibrosis than those in the group with highest elasticity (≥37.93 kPa). An inverse linear association was observed between renal elasticity increment and moderate-to-severe renal fibrosis risk.

CONCLUSION

There is a negative linear association between increased renal elasticity and moderate-to-severe renal fibrosis risk among CKD patients. Patients with diminished renal stiffness have a higher risk of moderate-to-severe renal fibrosis.

ADVANCES IN KNOWLEDGE

CKD patients with reduced renal stiffness have a higher likelihood of moderate-to-severe renal fibrosis.

Renal stiffness measured by shear wave elastography and its relationship with perirenal fat in patients with chronic kidney disease

PURPOSE

This study aimed to utilize shear wave elastography (SWE) to assess changes in renal stiffness and its influencing factors in patients with chronic kidney disease (CKD) across different estimated glomerular filtration rate (eGFR) categories. It also sought to determine the correlation between perirenal fat (PF) and renal stiffness at various stages of CKD.

METHODS

A total of 190 CKD patients and 50 healthy controls were evaluated. Clinical parameters, conventional renal ultrasound measurements, PF, and renal stiffness trends were assessed separately. Factors independently associated with renal stiffness and PF were further analyzed.

RESULTS

Renal parenchymal stiffness was significantly higher in the Albumin-CKD G1-2 (ALB-CKD G1-2) and CKD G3 groups than in the control group (p < 0.05). The parenchymal stiffness of the CKD G3 group was higher than that of the ALB-CKD G1-2 group (p < 0.05). The independent factors of renal parenchymal stiffness varied at different stages of disease development, with eGFR and PF being significant factors in the CKD G3 group. PF was elevated in the ALB-CKD G1-2 and CKD G3 groups compared to the control group, and the independent factors of PF varied across different stages, although waist circumference remained a common factor.

CONCLUSION

Using SWE to detect renal elastic moduli can effectively assess changes in renal stiffness in patients with CKD with varying eGFRs. PF is an independent factor of renal stiffness in patients with CKD G3, providing a foundation for early diagnosis and clinical treatment.

The Role of Superb Microvascular Imaging and Shear Wave Elastography in the Prediction of Hemorrhage Complications After Renal Parenchyma Biopsy

OBJECTIVES

The aim of study was to evaluate the diagnostic utility of the renal parenchyma elasticity with the shear wave elastography (SWE) and microvascularization with the superb microvascular imaging (SMI) technique before kidney biopsy and to predict the complication of hemorrhage before kidney biopsy.

METHODS

A total of 75 patients were included in the prospective study. Before the biopsy, vascularity features of the kidney parenchyma in the area to be biopsied were assessed by SMI and parenchymal stiffness by SWE and were examined by 2 independent radiologists.

RESULTS

A statistically significant difference was found in the SMI and SWE values between the groups with and without hematoma and hematuria when compared with the Student t test and Mann-Whitney U test ( P < 0.05). The SWE hardness cutoff value, which maximizes the prediction of the development of hematuria, was found to be 18.40 kPa, and the sensitivity and specificity values were 84.4% and 62.8%, respectively. In SMI vascularity index values, the cutoff value was found to be 0.247410800 kPa, and sensitivity and specificity values were 81.3% and 83.7%, respectively. The cutoff value of the SMI vascularity index values that maximized the prediction of hematoma development was 0.297009650, and the sensitivity and specificity values were 87% and 87%, respectively.

CONCLUSIONS

We believe that evaluating and standardizing the microvascularization and elasticity of the kidney parenchyma before a percutaneous kidney biopsy will be potentially useful as a guiding method in the prediction of postbiopsy hemorrhage development.

Advances in imaging techniques to assess kidney fibrosis

As a sign of chronic kidney disease (CKD) progression, renal fibrosis is an irreversible and alarming pathological change. The accurate diagnosis of renal fibrosis depends on the widely used renal biopsy, but this diagnostic modality is invasive and can easily lead to sampling error. With the development of imaging techniques, an increasing number of noninvasive imaging techniques, such as multipara meter magnetic resonance imaging (MRI) and ultrasound elastography, have gained attention in assessing kidney fibrosis. Depending on their ability to detect changes in tissue stiffness and diffusion of water molecules, ultrasound elastography and some MRI techniques can indirectly assess the degree of fibrosis. The worsening of renal tissue oxygenation and perfusion measured by blood oxygenation level-dependent MRI and arterial spin labeling MRI separately is also an indirect reflection of renal fibrosis. Objective and quantitative indices of fibrosis may be available in the future by using novel techniques, such as photoacoustic imaging and fluorescence microscopy. However, these imaging techniques are susceptible to interference or may not be convenient. Due to the lack of sufficient specificity and sensitivity, these imaging techniques are neither widely accepted nor proposed by clinicians. These obstructions must be overcome by conducting technology research and more prospective studies. In this review, we emphasize the recent advancement of these noninvasive imaging techniques and provide clinicians a continuously updated perspective on the assessment of kidney fibrosis.

Diagnostic utility of two-dimensional shear wave elastography in nephropathic dogs and its correlation with renal contrast-enhanced ultrasound in course of acute kidney injury

Aims of our study were to evaluate the feasibility and diagnostic value of two-dimensional shear wave elastography in dogs with acute kidney injury, chronic kidney disease, and acute on chronic kidney disease, its correlation with renal functional (creatinine, urea), and prognostic parameters (serum calcium-phosphorus product, urinary output), and with contrast-enhanced ultrasound (qualitative and quantitative evaluation). The study was prospective. A group of healthy (Group A) and a group of nephropathic dogs (Group B) were included. Shear wave elastography was performed on the left kidney of the subjects of both groups; contrast-enhanced ultrasound was performed only in dogs with acute kidney injury and acute on chronic kidney disease. Sixty-four dogs were included (Group A, n=24; Group B, n=40). The renal stiffness values were significantly higher in Group B than Group A; optimal cut-off stiffness values for detection of renal pathology were: ≥1.51 m/sec (area under the curve, 0.84; 95% confidence interval 0.74-0.94) and ≥6.75 kPa (area under the curve, 0.84; 95% confidence interval 0.73-0.94). For contrast-enhanced ultrasound, a significant positive correlation was found between renal stiffness, area under the curve, and wash-out area under the curve values of cortex quantitative analysis. No correlations were found between renal stiffness and renal functional and prognostic parameters. Shear wave elastography showed diagnostic utility to detect renal abnormalities in dogs with acute kidney injury, chronic kidney disease and acute on chronic kidney disease, however, it could not differentiate between these different nephropathies.

Development of a multimodal kidney age prediction based on automatic segmentation CT image in patients with normal renal function

Background

For decades, description of renal function has been of interest to clinicians and researchers. Serum creatinine (Scr) and estimated glomerular filtration rate (eGFR) are familiar but also limited in many circumstances. Meanwhile, the physiological volumes of the kidney cortex and medulla are presumed to change with age and have been proven to change with decreasing kidney function.

Methods

We recruited 182 patients with normal Scr levels between October 2021 and February 2022 in Peking Union Medical College Hospital (PUMCH) with demographic and clinical data. A 3D U-Net architecture is used for both cortex and medullary separation, and volume calculation. In addition, we included patients with the same inclusion criteria but with diabetes (PUMCH-DM test set) and diabetic nephropathy (PUMCH-DN test set) for internal comparison to verify the possible clinical value of "kidney age" (K-AGE).

Results

The PUMCH training set included 146 participants with a mean age of 47.5 ± 7.4 years and mean Scr 63.5 ± 12.3 μmol/L. The PUMCH test set included 36 participants with a mean age of 47.1 ± 7.9 years and mean Scr 66.9 ± 13.0 μmol/L. The multimodal method predicted K-AGE approximately close to the patient's actual physiological age, with 92% prediction within the 95% confidential interval. The mean absolute error increases with disease progression (PUMCH 5.00, PUMCH-DM 6.99, PUMCH-DN 9.32).

Conclusion

We established a machine learning model for predicting the K-AGE, which offered the possibility of evaluating the whole kidney health in normal kidney aging and in disease conditions.

Diagnostic assessment of two-dimensional shear wave elastography in relation to dimethyl arginine levels in dogs with chronic kidney disease

BACKGROUND

In veterinary medicine, previous studies regarding the diagnostic performance of shear wave elastography (SWE) in chronic kidney disease (CKD) are not consistent with each other. Moreover, there has been no study evaluating the relationship between symmetric dimethyl arginine (SDMA) concentration and renal shear wave velocity (SWV) using two-dimensional SWE (2D SWE) in dogs with CKD.

OBJECTIVES

This study aimed to evaluate the diagnostic capability of 2D SWE in dogs with CKD and to assess the relationship between renal SWV and SDMA concentration.

METHODS

Dogs with healthy kidneys and dogs with CKD underwent 2D SWE and SDMA assay. Renal stiffness was estimated as renal SWV in m/s.

RESULTS

SDMA concentration had a weak positive correlation with the left (r = 0.338, p = 0.022) and right renal SWV (r = 0.337, p = 0.044). Renal SWV was not significantly different between healthy kidney and CKD groups in the left (p = 0.085) and right (p = 0.171) kidneys.

CONCLUSIONS

2D SWE may could not distinguish between dogs with healthy kidney and dogs with early stage of CKD, but it would be useful for assessing the serial change of renal function in dogs.

Diagnostic performance of renal cortical elasticity by supersonic shear wave imaging in pediatric glomerular disease

PURPOSE

To explore the diagnostic performance of renal cortical elasticity expressed by Young's modulus (YM) using the supersonic shear wave imaging (SSI) technique in pediatric glomerular disease.

MATERIALS AND METHODS

Seventy-one children with glomerular disease confirmed by renal biopsy and sixty healthy volunteers were enrolled in this study. Conventional and SSI ultrasound examinations were performed in all individuals for both kidneys. We measured renal length, renal width, renal thickness, parenchyma thickness, interlobar arterial resistive index (RI) and the YM of the middle and lower pole.

RESULTS

Regardless of which pole and which side of the kidney, the YM in the disease group was significantly higher than that in the control group (P < 0.001). The YM of the middle pole in the left kidney demonstrated the largest AUC (0.936, P < 0.001), and the corresponding cut-off value was 15.48 kPa with a sensitivity of 87.3% and a specificity of 86.7%. There was no significant difference in the YM among different pathological types of pediatric glomerular disease in the disease group, and the same in different grades of patients with Immunoglobulin A (IgA) nephropathy by Lee classification and the Oxford Classification as well as Henoch-Schonlein purpura nephritis (HSPN) by International Study of Kidney Disease in Children (ISKDC) classification (P > 0.05). We found positive but weak correlations between the YM and renal length (r = 0.299, P = 0.001), renal width (r = 0.408, P < 0.001), renal thickness (r = 0.299, P = 0.001), and parenchyma thickness (r = 0.212, P = 0.015), whereas the YM had no significant correlations with age, sex, BMI, interlobar arterial RI, and laboratory findings (P > 0.05).

CONCLUSIONS

SSI technology is a non-invasive and feasible method for the diagnosis of pediatric glomerular disease. However, SSI did not show good performance in distinguishing different pathological types and disease grades in our study.

The value of shear wave elasticity and shear wave dispersion imaging to evaluate the viscoelasticity of renal parenchyma in children with glomerular diseases

BACKGROUND

To study the value of shear wave elasticity and shear wave dispersion imaging to evaluate the viscoelasticity of renal parenchyma in children with glomerular diseases.

METHODS

Forty-three children with glomerular diseases were prospectively evaluated by shear wave elasticity (SWE) and shear wave dispersion imaging (SWD); 43 healthy volunteers served as the control group. The shear wave velocities (SWV) and the dispersion slopes were measured at the upper, middle, and lower poles of both kidneys. The analysis of mean SWV and mean dispersion slope in control and patient groups was used to further evaluate the value of SWE and SWD in the viscoelasticity of renal parenchyma in children with glomerular disease.

RESULTS

The mean SWV in children with glomerular disease was higher than that in the healthy control group (1.61 ± 0.09 m/s vs. 1.43 ± 0.07 m/s, p < 0.001). Compared with healthy group, the mean dispersion slope in children with glomerular disease was significantly increased (13.5 ± 1.39 (m/s)/kHz vs. 12.4 ± 1.40 (m/s)/kHz, p < 0.001). Correlation analysis showed absence of correlation between the SWV and dispersion slope of occult blood, serum creatinine, 24-h urine protein, blood albumin, BMI and ROI box depth of children with glomerular disease.

CONCLUSIONS

The present study shows that it is feasible to use SWE and SWD to evaluate the difference of viscoelasticity of the renal parenchyma between healthy children and those with glomerular disease.

Diagnostic Efficacy of Renal 2-D Shear Wave Elastography in Familial Mediterranean Fever Disease

ABSTRACT

The aims of this study were to evaluate the kidneys of patients with familial Mediterranean fever (FMF) noninvasively and quantitatively using 2-D shear wave elastography (SWE) and to reveal the diagnostic efficacy of SWE in FMF-induced renal involvement. Healthy controls, FMF patients, and FMF patients with proteinuria were included in the study, and differences in renal stiffness values between the groups were examined. In addition, a relationship between age, sex, height, weight, body mass index, serum erythrocyte sedimentation rate, C-reactive protein, glomerular filtration rate, and renal stiffness values was evaluated. A total of 120 subjects, including 60 controls, 41 FMF patients without proteinuria, and 19 FMF patients with proteinuria, were enrolled in the study. Renal stiffness values were found to be significantly higher in the group with FMF compared with the control group. In addition, the values in the proteinuria group were higher than both the control group and FMF patients without proteinuria ( P < 0.001). A significant positive correlation was found between the renal stiffness value and C-reactive protein. According to receiver operating characteristic analysis, the mean renal stiffness value was 7.905 kPa or greater to determine FMF-induced proteinuria. The current study shows that renal stiffness values were higher in FMF patients compared with the normal population and the values showed further increase in the presence of proteinuria, which indicates a more advanced stage of renal involvement of the disease. These findings reveal that SWE can be used as a noninvasive diagnostic tool in the diagnosis, follow-up, and evaluating the severity of FMF.

Comparison of sound touch elastography and quantification for assessing the renal pathologic changes in patients with proteinuria

OBJECTIVE

Sound touch elastography (STE) and sound touch quantification (STQ) are novel imaging methods to evaluate tissue stiffness. This study aims to investigate renal stiffness in patients with chronic kidney disease (CKD) by STE and STQ, using renal biopsy as 'gold standard'.

METHODS

Between 2019 January and 2022 June, 60 patients who underwent renal biopsy for proteinuria (cases) and 45 healthy volunteers (controls) at our hospital were included in this study. The maximum and mean elastic modulus (Emax, Emean) of region of interest in right kidney were measured by STE and STQ techniques. Biochemical profiles and renal biopsy findings were recorded.

RESULTS

Both Emax and Emean measured by STE were significantly different between cases and controls. ROC analysis of STE measurements revealed using a cutoff of 13.53 kPa for Emax and 10.16 kPa for Emean, the area under the curve (AUC) to distinguish nephropathy from healthy was 0.718 and 0.744. Analysis of ROC for STQ measurements showed that using a cutoff value of 15.87 kPa for Emax and 9.95 kPa for Emean, the AUC for the nephropathy was 0.612 and 0.569. Emax and Emean values were significantly different among CKD patients with mild, moderate and severe pathological stage. The Emax value for STE was positively related to Scr, β2-MG (r = 0.257, 0.292, p < 0.05).

CONCLUSION

Both STE and STQ are non-invasive, feasible methods to quantitatively evaluate renal stiffness. STE is more effective than STQ in the diagnosis of CKD patients with proteinuria.

CRITICAL RELEVANCE STATEMENT

Sound touch elastography is more effective than sound touch quantification in the diagnosis of chronic kidney disease patients with proteinuria.

KEY POINTS

• Emax and Emean measured by STE were different between cases and controls. • Emax and Emean were different among CKD patients with different pathological stages. • The Emax value for STE was positively related to serum creatinine, β2-microglobulin.

Utility of shear wave-based ultrasound elastography in chronic kidney disease and related pathological quantitative analysis

OBJECTIVES

The purpose of this study was to investigate the effects of tissue fibrosis and microvessel density on shear wave-based ultrasound elastography (SWUE) of chronic kidney disease (CKD). In addition, we were looking to see whether SWUE could predict stage of CKD, correlating with the histology on kidney biopsy.

METHODS

Renal tissue sections from 54 patients diagnosed with suspected CKD were subjected to immunohistochemistry (CD31 and CD34), and the degree of tissue fibrosis was assessed using Masson staining. Before renal puncture, both kidneys were examined using SWUE. Comparative analysis was used to assess the correlation between SWUE and microvessel density, and between SWUE and the degree of fibrosis.

RESULTS

Fibrosis area according to Masson staining (p < 0.05) and integrated optical density (IOD) (p < 0.05) were positively correlated with CKD stage. The percentage of positive area (PPA) and IOD for CD31 and CD34 were not correlated with CKD stage (p > 0.05). When stage 1 CKD was removed, PPA and IOD for CD34 were negatively correlated with CKD stage (p < 0.05). Masson staining fibrosis area and IOD were not correlated with SWUE (p > 0.05), PPA and IOD for CD31 and CD34 were not correlated with SWUE (p > 0.05) and, finally, no correlation between SWUE and CKD stage was found (p > 0.05).

CONCLUSION

The diagnostic value of SWUE for CKD staging was very low. The utility of SWUE in CKD was affected by many factors and its diagnostic value was limited.

KEY POINTS

• There was no correlation between SWUE and the degree of fibrosis, or between SWUE and microvessel density among patients with CKD. • There was no correlation between SWUE and CKD stage and the diagnostic value of SWUE for CKD staging was very low. • The utility of SWUE in CKD is affected by many factors and its value was limited.

A Case of Shear Wave Velocity Reflecting the Disease Activity in Glomerulonephritis

Ultrasound elastography can measure tissue elasticity using the shear wave velocity (SWV). Evaluating disease activity with elastography instead of renal biopsy may be less invasive. However, to the best of our knowledge, although there are studies comparing different glomerular diseases using SWV, there are no reports that have measured glomerulonephritis longitudinally from the acute phase of the disease. This study aimed to assess whether SWV reflects disease activity in glomerulonephritis, and we continued to observe children with post-streptococcal acute glomerulonephritis (PSAGN) from the acute phase to over a year later. In this case, a 6-year-old boy diagnosed with PSAGN had impaired renal function, and was admitted and tested. He was placed in a prone resting position and measurements were taken from the back. SWV was measured ≥50 times at each examination, and the mean was calculated when the net amount of effective SWV was ≥50%. The tests were performed once in the acute phase and thrice during the recovery phase for 13 months. SWV was found to be significantly lower in the recovery period than during the disease onset, and continued to stay lower at each test during the recovery period (P < 0.02). In conclusion, this indicated that SWV fluctuated similarly to the disease activity of glomerulonephritis; therefore, we suggest using SWV measurement to estimate the disease activity in glomerulonephritis in children. Although more clinical cases are needed, SWV measurement is a noninvasive and reproducible imaging modality to estimate the disease activity in glomerulonephritis.

Ultrasound elastography in chronic kidney disease: a systematic review and meta-analysis

Ultrasound elastography (USE) is a noninvasive technique for assessing tissue elasticity, and its application in nephrology has aroused growing interest in recent years. The purpose of this article is to systematically review the clinical application of USE in patients with chronic kidney disease (CKD), including native and transplanted kidneys, and quantitatively investigate differences in elasticity values between healthy individuals and CKD patients. Furthermore, we provide a qualitative analysis of the studies included, discussing the potential interplay between renal stiffness, estimated glomerular filtration rate, and fibrosis. In January 2022, a systematic search was carried out on the MEDLINE (PubMed) database, concerning studies on the application of USE in patients with CKD, including patients with transplanted kidneys. The results of the included studies were extracted by two independent researchers and presented mainly through a formal narrative summary. A meta-analysis of nine study parts from six studies was performed. A total of 647 studies were screened for eligibility and, after applying the exclusion and inclusion criteria, 69 studies were included, for a total of 6728 patients. The studies proved very heterogeneous in terms of design and results. The shear wave velocity difference of - 0.82 m/s (95% CI: - 1.72-0.07) between CKD patients and controls was not significant. This result agrees with the qualitative evaluation of included studies that found controversial results for the relationship between renal stiffness and glomerular filtration rate. On the contrary, a clear relationship seems to emerge between USE values and the degree of fibrosis. At present, due to the heterogeneity of results and technical challenges, large-scale application in the monitoring of CKD patients remains controversial.

Assessment of Renal Fibrosis in Patients With Chronic Kidney Disease Using Shear Wave Elastography and Clinical Features: A Random Forest Approach

OBJECTIVE

Renal fibrosis is the common pathological hallmark of chronic kidney disease (CKD) progression. In this study, a random forest (RF) classifier based on 2-D shear wave elastography (SWE) and clinical features for the differential severity of renal fibrosis in patients with CKD is proposed.

METHODS

A total of 162 patients diagnosed with CKD who underwent 2-D SWE and renal biopsy were prospectively enrolled from April 2019 to December 2021 and then randomized into training (n = 114) and validation (n = 48) cohorts at a ratio of 7:3. The least absolute shrinkage and selection operator (LASSO) regression and recursive feature elimination for support vector machines (SVM-RFE) algorithm were employed to select renal fibrosis-related features from clinical information and elastosonographic findings. An RF model was subsequently constructed using the aforementioned informative parameters in the training cohort and evaluated in terms of discrimination, calibration and clinical utility in both cohorts.

RESULTS

The LASSO and SVM-RFE analyses revealed that age, sex, blood urea nitrogen, renal resistive index, hypertension and the 2D-SWE value were independent risk variables associated with renal fibrosis severity. The established RF model incorporating these six variables exhibited fine discrimination in both the derivation (area under the curve [AUC]: 0.84, 95% confidence interval [CI]: 0.76-0.91) and validation (AUC: 0.88, 95% CI: 0.77-0.98) cohorts. Moreover, the calibration curve revealed satisfactory predictive accuracy, and the decision curve analysis revealed a significant clinical net benefit.

CONCLUSION

The developed RF model, via a combination of the 2-D SWE value and clinical information, indicated satisfactory diagnostic performance and clinical practicality toward differentiating moderate-severe from mild renal fibrosis, which may provide critical insight into risk stratification for patients with CKD.

Shear Wave Elastography for Assessment of Biopsy-Proven Renal Fibrosis: A Systematic Review and Meta-analysis

The purpose of this meta-analysis was to evaluate the diagnostic performance of shear wave elastography (SWE) for the staging of renal fibrosis in patients with chronic kidney disease (CKD). Classification of CKD into mild, moderate and severe fibrosis was based on renal biopsy pathology (glomerulosclerosis, tubulointerstitial injury and vascular sclerosis). The Cochrane Library, Medline, PubMed, Web of Science, EMBASE and CNKI databases were searched from January 1, 2009, to April 20, 2022. Pooled sensitivity, specificity, diagnostic odds ratio and area under the receiver operating characteristic curve (AUROC) were calculated using random effects models. A total of 1394 patients from 14 studies were included in the final analysis. For mild, moderate and severe renal fibrosis, SWE had a sensitivity of 0.79 (95% confidence interval [CI]: 0.67-0.88), 0.73 (95% CI: 0.65-0.80) and 0.87 (95% CI: 0.71-0.95); a specificity of 0.82 (95% CI: 0.75-0.87), 72% (95% CI: 0.67-0.77) and 0.83 (95% CI: 0.80-0.86); an AUROC of 0.87 (95% CI: 0.84-0.90), 0.78 (95% CI: 0.75-0.82) and 0.86 (95% CI: 0.82-0.88); and a diagnostic odds ratio of 17 (95% CI: 7-43), 7 (95% CI: 4-12) and 34 (95% CI: 13-88), respectively. Meta-regressions revealed that the publication date, system used and number of valid measurements of SWE were the main causes of heterogeneity. SWE is a good technique for diagnosing mild and severe renal fibrosis, as well as a fair technique for diagnosing moderate fibrosis.

A methodological study of 2D shear wave elastography for noninvasive quantitative assessment of renal fibrosis in patients with chronic kidney disease

PURPOSE

To determine the optimal measurement method of 2D shear wave elastography (2D-SWE) for noninvasive quantitative assessment of renal fibrosis in chronic kidney disease (CKD) patients.

METHODS

A total of 190 CKD patients were enrolled for 2D-SWE of right kidney. The success rates, coefficients of variation (CV), and pathological correlation of different measurement sites, body positions, and depths were compared.

RESULTS

(1) Measurement sites: Success rate in the middle part (100%) was higher than that in the lower pole (97.3%, P > 0.05). CV in the middle part (10.2%) was lower than that in the lower pole (16.4%, P < 0.05). Pathological correlation of the middle part (r =  - 0.452, P < 0.05) was higher than that of the lower pole (r = 0.097, P > 0.05). (2) Body positions: Success rate in left lateral decubitus position (100%) was higher than that in supine (99.4%, P > 0.05) and prone position (99.4%, P > 0.05). CV was lowest (11.9%) and pathological correlation was highest (r = -0.256, P < 0.05) in prone position. (3) Measurement depths: Success rate at depth < 4 cm (100%) was higher than that at depth ≥ 4 cm (98.8%, P > 0.05). CV at depth < 4 cm (11.1%) was lower than that at depth ≥ 4 cm (14.4%, P < 0.05). Pathological correlation at depth < 4 cm (r =  - 0.303, P < 0.05) was higher than that at depth ≥ 4 cm (r =  - 0.156, P > 0.05).

CONCLUSION

The optimal measurement method of 2D-SWE for renal fibrosis assessment was prone position, renal middle part, and measurement depth < 4 cm.

Nomogram based on high-frequency shear wave elastography (SWE) to evaluate chronic changes after kidney transplantation

OBJECTIVES

To construct a nomogram with high-frequency shear wave elastography (SWE) as a noninvasive method to accurately assess chronic changes in renal allografts.

METHODS

A total of 191 renal transplantation patients (127 cases in the training group and 64 cases in the verification group) were included in this study. All patients received conventional ultrasound and high-frequency SWE examination, followed directly by biopsy the next day. The chronic changes were divided into mild, moderate, and severe. Multivariate logistic analyses were used to select significant variables, which were used to develop the nomogram. Nomogram models were assessed by receiver operating characteristic (ROC) curves, calibration plots, and decision curve analysis (DCA).

RESULTS

The cutoff value of SWE in mild, moderate, and severe chronic changes was 18.9, 22.5, and 27.6 kPa, respectively. The areas under the curve (AUCs) of SWE in the differential diagnosis of mild and moderate to severe chronic changes and mild to moderate and severe chronic changes were 0.817 and 0.870, respectively. Multivariate analysis showed that time since transplantation, proteinuria, glomerular filtration rate, echogenicity, and SWE were independent diagnostic factors for moderate to severe chronic changes (all p < 0.05); thus, a nomogram was successfully developed. The AUCs of the nomogram in the training and validation groups were 0.905 and 0.938, respectively. The high agreement between the model predictions and the actual observations was confirmed by calibration plot and DCA.

CONCLUSIONS

Based on SWE, the nomogram provided an insightful and applicable tool to evaluate chronic changes in renal allografts.

KEY POINTS

• In kidney transplantation, compared with acute changes, chronic changes are significantly correlated with cortical stiffness. • SWE shows good performance in identifying mild to moderate and severe chronic changes, with an AUC of 0.870. • Time since transplantation, proteinuria, glomerular filtration rate, echogenicity, and SWE are independent diagnostic factors for moderate to severe chronic changes in renal allografts.

An evaluation with shear wave elastography of kidney elasticity in patients with familial Mediterranean fever

PURPOSE

To investigate the changes in kidney elasticity in patients with familial Mediterranean fever using the non-invasive diagnostic method of shear wave elastography (SWE).

METHODS

The kidney elasticity of 35 FMF patients and 23 healthy control subjects was evaluated with SWE. The relationships were evaluated of the SWE values with eGFR, microproteinuria, FMF severity score, number of attacks per month, and colchicine doses of the FMF patients.

RESULTS

The kidney stiffness and velocity values of the FMF patients were found to be higher than those of the control group (p < 0.001). A negative correlation was found between the renal stiffness and velocity values and the colchicine dose (r = -0.48, p = 0.004, and r = -0.50, p = 0.003, respectively).

CONCLUSION

The results of the current study demonstrated that the SWE values of the FMF patients were significantly higher than those of the control group. SWE can be used as an alternative method in the follow up of FMF patients. In addition, a negative correlation was determined between the colchicine dose and renal stiffness. This suggests that SWE values could be used in the adjustments of colchicine doses. However, there is a need for further studies with greater numbers of patients to support this hypothesis.

Noninvasive evaluation of IgA nephropathy fibrosis using Doppler ultrasound

In this study, we aimed to explore the clinical value of routine color ultrasound parameters in the evaluation of tubular atrophy and interstitial fibrosis (TA/IF) in IgA nephropathy (IgAN). We enrolled 725 patients with IgAN who underwent renal biopsy at the First Affiliated Hospital of Anhui Medical University between January 2019 and May 2022. Examinations were performed to measure the routine ultrasound renal parameters and renal biopsy was done within next three days. Univariate and multivariate analyses were used to determine the correlates and the independent predictors of TA/IF. Simultaneously, a nomogram based on risk indicators was created to predict TA/IF. Univariate and multivariate analyses showed that sex (p < 0.001, OR = 2.538, 95%CI: 1.739–3.734), renal length (p < 0.001, OR = 0.927, 95%CI: 0.905–0.95), resistive index of main renal artery (p = 0.037, OR = 1.891, 95%CI: 1.027–3.426), peak systolic velocity of segmental renal artery (p = 0.58, OR = 0.975, 95%CI: 0.399–0.841), and cortex echogenicity (p < 0.001, OR = 3.448, 95%CI: 2.382–5.018) were independent predictors of TA/IF in IgAN nomograms, with a good C-index of 0.765 (95%CI = 0.727–0.803). Analyses of the calibration charts show that nomograms have good performance and clinical applicability. In our study, renal color ultrasound parameters correlated well with TA/IF in IgAN. By establishing a conventional color ultrasound prediction model, we can accurately gauge the extent of TA/IF in patients with IgAN for clinical applications.

Non-Invasive Evaluation of Kidney Elasticity and Viscosity in a Healthy Cohort

Introduction: There is currently a lack of published data on kidney elasticity and viscosity. Non-invasive techniques, such as two-dimensional shear-wave elastography (2D-SWE PLUS) and viscosity plane-wave ultrasound (Vi PLUS), have surfaced as new detection methods, which, thanks to efficient processing software, are expected to improve renal stiffness and viscosity measurements. This study aims to be the first one to assess the normal range values in normal renal function subjects and to investigate the factors that impact them. Methods: We conducted a cross-sectional study employing 50 participants (29 women and 21 men) with a mean age of 42.22 ± 13.17, a mean estimated glomerular filtration rate (eGFR) of 97.12 ± 11 mL/min/1.73 m2, a mean kidney length of 10.16 ± 0.66 cm, and a mean body mass index (BMI) of 24.24 ± 3.98. With a C6-1X convex transducer and the Ultra-FastTM software available on the Hologic Aixplorer Mach 30 ultrasound system, we acquired five measurements of renal cortical stiffness and viscosity (achieved from five distinct images in the middle part of the subcapsular cortex) from each kidney. The ten measurements’ median values correlated with the participant’s demographical, biological, and clinical parameters. Results: The mean kidney elasticity was 31.88 ± 2.89 kiloPascal (kPa), and the mean viscosity was 2.44 ± 0.57 Pascal.second (Pa.s) for a mean measurement depth 4.58 ± 1.02 cm. Renal stiffness seemed to be influenced by age (r = −0.7047, p < 0.0001), the measurement depth (r = −0.3776, p = 0.0075), and eGFR (r = 0.6101, p < 0.0001) but not by BMI (r = −0.2150, p = 0.1338), while viscosity appeared to be impacted by age (r = −0.4251, p = 0.0021), eGFR (r = 0.4057, p = 0.0038), the measurement depth (r = −0.4642, p = 0.0008), and BMI (r = −0.3676, p = 0.0086). The results of the one-way ANOVA used to test the differences in the variables among the three age sub-groups are statistically significant for both 2D-SWE PLUS (p < 0.001) and Vi PLUS (p = 0.015). The method found good intra-operator reproducibility for the 2D-SWE PLUS measurements, with an ICC of 0.8365 and a 95% CI of 0.7512 to 0.8990, and for the Vi PLUS measurements, with an ICC of 0.9 and a 95% CI of 0.8515 to 0.9397. Conclusions: Renal stiffness and viscosity screening may become an efficacious, low-cost way to gather supplemental diagnostic data from patients with chronic kidney disease (CKD). The findings demonstrate that these non-invasive methods are highly feasible and not influenced by gender and that their values correlate with renal function and decrease with age progression. Nevertheless, more research is required to ascertain their place in clinical practice.

Are the Currently Available Elastography Methods Useful in the Assessment of Chronic Kidney Disease? A Systematic Review and a Meta-Analysis

Background: We require an quantitative imaging technique for the diagnosis and assessment of chronic kidney disease (CKD). Renal elastography has been widely used in recent years in different studies; however, the results across them are not consistent and, as a result, we conducted a meta-analysis of the published literature on this topic. Methods: The databases of PubMed, Medscape, Medline were searched for all studies published in English from 2010 until November 2021 that evaluated kidney shear wave speed (SWS) by elastography in patients with CKD. Trial design, methodological information, patient characteristics, interventions, results, and outcome data were all collected from each study according to a set protocol. Results: We found 37 publications, yet only 18 studies that utilized point shear wave elastography (Virtual Touch Quantification—VTQ system) were compared because the values achieved using different types of elastography are not evaluable. Finally, 1995 attendees (1241 patients with CKD versus 781 healthy subjects as the control group) were included. When comparing mean values of kidney SWS between studies we found increased heterogeneity Q = 513.133; DF = 10; p < 0001, I2 (inconsistency) = 98.12% (95% CI for I2 97.52–98.57%). With a standardized mean difference of −0.216, patients with CKD have a lower kidney SWS than healthy controls. A positive association between kidney SWS and eGFR was also discovered across the presented studies, with a pooled correlation coefficient of 0.38 (Z = 10.3, p < 0.001), Q = 73.3, DF = 5, p < 000.1, I2 = 93.18% (95% CI for I2 87.86 to 96.18). The pooled area under the ROC curve for kidney SWS to predict chronic kidney disease was 0.831 (95% CI, p < 0.001), Q = 28.32, DF = 6, p = 0.0001, I2 = 78.8% (95% CI for I2 56.37 to 89.72). In the four articles that used the Elast-PQ method, the data presented were insufficient for statistical analysis: area under the curve (AUC) values are used to compare distinct characteristics (differentiating kidney SWS between mildly and moderately impaired kidneys, between non-diabetic/prediabetic/diabetic patients, or kidney SWS between the CKD and control group), therefore not being suitable for further evaluation. Conclusions: The results show that patients with CKD have a lower kidney SWS than healthy controls. However, the number of studies involving renal elastography that have been published is limited and show an increased heterogeneity. Further research is needed to determine which factors actually influence kidney SWS in CKD patients and, as a result, to specify the role and indication of renal elastography in clinical practice.

Evaluation of renal fibrosis in patients with chronic kidney disease by shear wave elastography: a comparative analysis with pathological findings

PURPOSE

To explore the elastic values obtained by shear wave elastography (SWE) in assessing renal fibrosis in chronic kidney disease (CKD).

METHODS

One hundred and twenty-four patients with CKD who underwent renal biopsy were prospectively enrolled between April 2019 and June 2021. SWE was performed to measure the renal cortex stiffness, presented as SWE parameters, including the minimum, mean, and maximum elasticity (namely Emin, Emean, and Emax). Then, the patients with different kidney pathological impairment (mild, moderate, and severe groups) were compared in SWE elasticity and the discriminative capacity was also analyzed.

RESULTS

For the pathology impaired grade, SWE parameter was significantly reduced in the moderately and severely impaired group than the mild one. Emax parameter achieved the best discriminative ability toward differentiating moderate-severe impairment from mild one, yielding an area under the curve (AUC) of 0.764 (95%CI: 0.681-0.848). Regarding interstitial fibrosis/tubular atrophy and global glomerular sclerosis, the Emax values were significantly reduced across the group of patients with moderate grade compared to those with mild grade. Patients in severe group were also with reduced elastic value than those in mild one, while the difference was non-significant in interstitial fibrosis/tubular atrophy but a borderline statistical significance was achieved in global glomerular sclerosis. For grade of vessel wall thickening, patients in moderate (33.04 ± 9.86 kPa, P = 0.009) and severe (31.42 ± 9.16 kPa, P < 0.001) group were with significantly lower elastic value compared with those in the mild one (39.58 ± 9.67 kPa). The SWE parameter was linearly reduced as grade of vessel wall thickening elevated (P for trend: < 0.001).

CONCLUSION

SWE derived elastic values reduced as pathology grade of renal fibrosis or grade of vessel wall thickening progresses in patients with CKD, which may be attributed to renal hypo-perfusion rather than tubulo-interstitial fibrosis progression.

Does Early Diabetic Kidney Damage Alter Renal Elasticity? An Ultrasound-Based, Two-Dimensional Shear Wave Elastography Study

Objective

Kidney damage caused by type 2 diabetes mellitus (T2DM) can reduce renal elasticity. Limited number of data exist indicating whether early kidney damage causes stiffening of renal tissue. This comparative study aims to assess kidney elasticity in T2DM patients with or without moderate albuminuria, using ultrasound-based two-dimensional shear wave velocity (2D-SWV) measurements.

Methods

Fifty-seven cases (40 T2D patients with stage 1 or 2 chronic kidney disease and 17 age- and sex-matched healthy controls) were included in this single-center prospective study. The T2DM patients were divided into those with moderate albuminuria (n=22) and those without albuminuria (n=18). Bilateral renal parenchymal 2D-SWV values were measured (separately) in the upper, middle, and lower kidney regions. Group data were compared using the t-test or Mann-Whitney-U test (whichever appropriate). Inter-observer agreement was assessed by deriving the intra-class correlation coefficient.

Results

There was no difference between the T2DM and control groups in terms of the median age [55.5 (50-62) vs. 55 (48.5-59.5) years, p=0.48] and sex ratio [18 (45%) males vs. 10 (58.8%) females, p=0.34]. The average regional 2D-SWV values were all similar between the groups (all p>0.05). The average 2D-SWV values were similar between the subgroups with and without albuminuria. The inter-observer agreement was good (intra-class correlation coefficient=0.66, 95% CI 0.19-0.88, p=0.006)

Conclusion

Kidney elasticity does not seem to be compromised in patients with diabetes and preserved estimated glomerular filtration rate with or without moderate albuminuria.

Renal Acoustic Radiation Force Impulse Elastography in Hypertensive Nephroangiosclerosis Patients

Objective: Hypertensive nephroangiosclerosis (HN) represents the second most common cause of chronic kidney disease. Kidney damage secondary to high blood pressure favors the appearance of serum and urinary changes, but also imaging, highlighted by ultrasonography (B-mode, Doppler, Acoustic Radiation Force Impulse Elastography). Acoustic Radiation Force Impulse Elastography (ARFI) represents a new imagistic method which characterizes renal stiffness in the form of shear wave velocity (SWV). Aim: This study aims to investigate renal stiffness in HN patients, and to assess the correlations between it and urinary albumin/creatinine ratio (UACR), estimated glomerular filtration rate (eGFR), and intrarenal resistive index (RRI). Material and Methods: This cross-sectional study was performed on a group of 80 HN patients and 50 healthy, sex and age-matched, as controls. UACR (urinary immunoturbidimetry), eGFR (Jaffe method), RRI, and renal SWV (Siemens Acuson 2000) were determined in all patients and controls. Data were expressed as mean ± standard deviation. Statistical analysis was done by means Pearson’s test and t-Student test, p values of less than 0.05 were considered statistically significant. Results: UACR, eGFR, RRI and SWV showed statistically significant differences between the HN patients and controls (p < 0.0001). In the hypertensive patients group, statistically significant correlations were observed between the SWV and UACR (r = −0.7633, p < 0.00001), eGFR (r = 0.7822, p = 0.00001), and RRI (r = −0.7978, p = 0.00001). Conclusions: Kidney sonoelastography characterizes imagistically the existence of intrarenal lesions associated with essential hypertension, offering a new diagnosis method for these patients.

Technical feasibility and correlations between shear-wave elastography and histology in kidney fibrosis in children

BACKGROUND

Ultrasound elastography has been suggested for assessing organ fibrosis.

OBJECTIVE

To study the feasibility of shear-wave elastography in children with kidney disease and the correlation between elasticity and kidney fibrosis in order to reduce the indications for kidney biopsy and its complications.

MATERIALS AND METHODS

Four operators measured kidney elasticity in children with kidney diseases or transplants, all of whom also had a renal biopsy. We assessed the feasibility and the intraobserver variability of the elasticity measurements for each probe used and each kidney explored. Then we tested the correlation between elasticity measurements and the presence of fibrosis.

RESULTS

Overall, we analyzed 95 children and adolescents, 31 of whom had renal transplant. Measurements with the convex probe were possible in 100% of cases. Linear probe analysis was only possible for 20% of native kidneys and 50% of transplants. Intraobserver variabilities ranged from moderate to high, depending on the probe and kidney studied. Elasticity was higher with the linear probe than with the convex probe (P<0.001 for left kidney and P=0.03 for right kidney). Measurements did not differ from one kidney to another in the same child. Elasticity and fibrosis were both higher in transplant patients (P=0.02 with convex probe; P=0.01 with linear probe; P=0.04 overall). There was no correlation between elasticity and fibrosis.

CONCLUSION

Of the devices used in this work, kidney elastography was more accurately analyzed with a convex probe. Our study did not identify any correlation between elasticity and kidney fibrosis.

Elastography ultrasound with machine learning improves the diagnostic performance of traditional ultrasound in predicting kidney fibrosis

BACKGROUND

Noninvasively predicting kidney tubulointerstitial fibrosis is important because it's closely correlated with the development and prognosis of chronic kidney disease (CKD). Most studies of shear wave elastography (SWE) in CKD were limited to non-linear statistical dependencies and didn't fully consider variables' interactions. Therefore, support vector machine (SVM) of machine learning was used to assess the prediction value of SWE and traditional ultrasound techniques in kidney fibrosis.

METHODS

We consecutively recruited 117 CKD patients with kidney biopsy. SWE, B-mode, color Doppler flow imaging ultrasound and hematological exams were performed on the day of kidney biopsy. Kidney tubulointerstitial fibrosis was graded by semi-quantification of Masson staining. The diagnostic performances were accessed by ROC analysis.

RESULTS

Tubulointerstitial fibrosis area was significantly correlated with eGFR among CKD patients (R = 0.450, P < 0.001). AUC of SWE, combined with B-mode and blood flow ultrasound by SVM, was 0.8303 (sensitivity, 77.19%; specificity, 71.67%) for diagnosing tubulointerstitial fibrosis (>10%), higher than either traditional ultrasound, or SWE (AUC, 0.6735 [sensitivity, 67.74%; specificity, 65.45%]; 0.5391 [sensitivity, 55.56%; specificity, 53.33%] respectively. Delong test, p < 0.05); For diagnosing different grades of tubulointerstitial fibrosis, SWE combined with traditional ultrasound by SVM, had AUCs of 0.6429 for mild tubulointerstitial fibrosis (11%-25%), and 0.9431 for moderate to severe tubulointerstitial fibrosis (>50%), higher than other methods (Delong test, p < 0.05).

CONCLUSION

SWE with SVM modeling could improve the diagnostic performance of traditional kidney ultrasound in predicting different kidney tubulointerstitial fibrosis grades among CKD patients.

Shear Wave Elastography: A Review on the Confounding Factors and Their Potential Mitigation in Detecting Chronic Kidney Disease

Early detection of chronic kidney disease is important to prevent progression of irreversible kidney damage, reducing the need for renal transplantation. Shear wave elastography is ideal as a quantitative imaging modality to detect chronic kidney disease because of its non-invasive nature, low cost and portability, making it highly accessible. However, the complexity of the kidney architecture and its tissue properties give rise to various confounding factors that affect the reliability of shear wave elastography in detecting chronic kidney disease, thus limiting its application to clinical trials. The objective of this review is to highlight the confounding factors presented by the complex properties of the kidney, in addition to outlining potential mitigation strategies, along with the prospect of increasing the versatility and reliability of shear wave elastography in detecting chronic kidney disease.

Novel Uses of Ultrasound to Assess Kidney Mechanical Properties

Ultrasound is a key imaging tool for evaluating the kidney. Over the last two decades, methods to measure the mechanical properties of soft tissues have been developed and used in clinical practice, although use in the kidney has not been as widespread as for other applications. The mechanical properties of the kidney are determined by the structure and composition of the renal parenchyma and perfusion characteristics. Because pathologic processes change these factors, the mechanical properties change and can be used for diagnostic purposes and for monitoring treatment or disease progression. Ultrasound-based elastography methods for evaluating the mechanical properties of the kidney use focused ultrasound beams to perturb the kidney and then high frame-rate ultrasound methods are used to measure the resulting motion. The motion is analyzed to estimate the mechanical properties. This review will describe the principles of these methods and discuss several seminal studies related to characterizing the kidney. Additionally, an overview of the clinical use of elastography methods in native and kidney allografts will be provided. Perspectives on future developments and uses of elastography technology along with other complementary ultrasound imaging modalities will be provided.

The association between renal elasticity evaluated by Real-time tissue elastography and renal fibrosis

BACKGROUND

The progression of chronic kidney disease (CKD) depends on the extent of fibrosis in the kidneys; however, a renal biopsy is necessary to evaluate the severity of renal fibrosis. Real-time tissue elastography (RTE), which measures heartbeat-induced tissue displacement, can assess the elasticity of organs. Here, we aimed to investigate the correlation between renal elasticity and the extent of fibrosis in renal biopsy samples.

METHODS

We investigated 29 consecutive patients who underwent a renal biopsy at Ehime University Hospital from February 2018 to August 2019. Renal fibrosis was categorized into three grades, mild (< 25%), moderate (25-50%), and severe (> 50%), based on the total affected area within the biopsy sample. The association between renal elasticity assessed by RTE and the grade of renal fibrosis was evaluated, and a receiver operating characteristic curve was used to distinguish the severity of renal fibrosis.

RESULTS

The mean age and estimated glomerular filtration rate (eGFR) were 58.8 years and 55.2 mL/min/1.73 m², respectively. The median urine protein-to-creatinine ratio was 1.24 g/gCr. The mean renal elasticity of mild, moderate, and severe renal fibrosis was 3.40, 3.98, and 4.77, respectively. Renal elasticity of native kidneys was significantly positively correlated with the grade of renal fibrosis (ρ = 0.529, P = 0.003). At the cutoff point of 3.81, the area under the curve, sensitivity, and specificity were 0.778, 68.4%, and 81.8%, respectively.

CONCLUSION

Real-time tissue elastography is a promising, non-invasive method for assessing renal fibrosis in patients with CKD.

Viscoelasticity measured by shear wave elastography in a rat model of nonalcoholic fatty liver disease: comparison with dynamic mechanical analysis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is rapidly becoming one of the most common liver diseases. Ultrasound elastography has been used for the diagnosis of NAFLD. However, clinical research on steatosis by elastography technology has mainly focused on steatosis with fibrosis or non-alcoholic steatohepatitis (NASH), while steatosis without fibrosis has been poorly studied. Moreover, the relationship between liver viscoelasticity and steatosis grade is not clear. In this study, we evaluated the degree of liver steatosis in a simple steatosis rat model using shear wave elastography (SWE).

RESULTS

The viscoelasticity values of 69 rats with hepatic steatosis were measured quantitatively by SWE in vivo and validated by a dynamic mechanical analysis (DMA) test. Pathological sections were used to determine the steatosis grade for each rat. The results showed that the elasticity values µ obtained by the two methods followed the same trend, and µ is significantly correlated with liver steatosis. The Pearson's correlation coefficients indicate that [Formula: see text] obtained by SWE is positively linear correlated with DMA (r = 0.628, p = 7.85 × 10-9). However, the viscosity values [Formula: see text] obtained by SWE were relatively independent of those obtained by DMA with a correlation coefficient of - 0.01. The combined Voigt elasticity measurements have high validity in the prediction of steatosis (S0 vs. S1-S4), with an AUROC of 0.755 (95% CI 0.6175-0.8925, p < 0.01) and the optimal cutoff value was 2.08 kPa with a sensitivity of 78% and specificity of 63%.

CONCLUSION

SWE might have the feasibility to be introduced as an auxiliary technique for NAFLD patients in clinical settings. However, the viscosity results measured by SWE and DMA are significantly different, because the two methods work in different frequency bands.

Advances of Contrast-Enhanced Ultrasonography and Elastography in Kidney Transplantation: From Microscopic to Microcosmic

Kidney transplantation is the best choice for patients with end-stage renal disease. To date, allograft biopsy remains the gold standard for revealing pathologic changes and predicting long-term outcomes. However, the invasive nature of transplant biopsy greatly limits its application. Ultrasound has been a first-line examination for evaluating kidney allografts for a long time. Advances in ultrasound in recent years, especially the growing number of studies in elastography and contrast-enhanced ultrasonography (CEUS), have shed new light on its application in kidney transplantation. Elastography, including strain elastography and shear wave elastography, is used mainly to assess allograft stiffness and, thus, predict renal fibrosis. CEUS has been used extensively in evaluating blood microperfusion, assessing acute kidney injury and detecting different complications after transplantation. Requiring the use of microbubbles also makes CEUS a novel method of gene transfer and drug delivery, enabling promising targeted diagnosis and therapy. In this review, we summarize the advances of elastography and CEUS in kidney transplantation and evaluate their potential efficiency in becoming a better complement to or even substitute for transplant biopsy in the future.

Renal tissue elasticity by acoustic radiation force impulse: A prospective study of healthy kidney donors

BACKGROUND

Some studies reported the correlations between renal parenchymal stiffness measured by transient elastography or acoustic radiation force impulse (ARFI) and the extent of interstitial fibrosis. This study was prospectively designed to evaluate the correlation between clinical, histological findings and the kidney shear wave velocity (SWV, m/s) assessed by ARFI elastography to identify factors affecting the kidney SWV in normal patients.

METHODS

Seventy-three adult living kidney transplantation donors were enrolled in our center between September 2010 and January 2013. Before transplantation, all donors were evaluated by ARFI elastography to identify the range of SWV in kidneys. Time-zero biopsies were performed on all graft kidneys before implantation.

RESULTS

Mean age of donors was 42.0 ± 11.3 years. The mean SWV and depth were 2.21 ± 0.58 m/s and 5.37 ± 1.06 cm. All histological findings showed mild degree of the Banff score, only grade I. In univariate analyses, the SWV was not associated with all histological parameters. Age (r = -0.274, P = .019) diastolic blood pressure (DBP, r = -0.255, P = .030) and depth for SWV measurement (r = -0.345, P = .003) were significantly correlated with the SWV. In multivariate linear regression analysis, age, gender, body mass index (BMI), and depth for SWV measurement were significantly correlated with the SWV (P = .003, .005, .002, and .004, respectively).

CONCLUSIONS

We demonstrated that all histological findings are not correlated with the SWV of donor kidney. Otherwise, factors influencing the kidney SWV assessed by ARFI elastography are age, gender, BMI, and depth for the SWV measurement in donors for kidney transplantation.

Shear wave elastography accurately detects chronic changes in renal histopathology

AIM

Renal biopsy is the gold standard for the histological characterization of chronic kidney disease (CKD), of which renal fibrosis is a dominant component, affecting its stiffness. The aim of this study was to investigate the correlation between kidney stiffness obtained by shear wave elastography (SWE) and renal histological fibrosis.

METHODS

Shear wave elastography assessments were performed in 75 CKD patients who underwent renal biopsy. The SWE-derived estimates of the tissue Young's modulus (YM), given as kilopascals (kPa), were measured. YM was correlated to patients' renal histological scores, broadly categorized into glomerular, tubulointerstitial and vascular scores.

RESULTS

Young's modulus correlates significantly with tubulointerstitial score (ρ = 0.442, P < .001) and glomerular score (ρ = 0.375, P = .001). Patients with no glomerular sclerosis showed lower mean YM measurements compared to those with glomerular sclerosis. The mean YM increased as the percentage of interstitial fibrosis and tubular atrophy increased. The area under the receiver operating characteristic curve (ROC) for SWE in differentiating between mildly and moderately impaired kidneys was 0.702.

CONCLUSION

Shear wave elastography accurately detects chronic renal damage resulting from glomerular sclerosis, interstitial fibrosis and tubular atrophy, using the optimal cut-off YM value of ≥5.81 kPa.

Two-Dimensional Shear Wave Elastography of Normal Soft Tissue Organs in Adult Beagle Dogs; Interobserver Agreement and Sources of Variability

Shear wave elastography (SWE) induces lateral shear wave through acoustic pulses of the transducer and evaluates tissue stiffness quantitatively. This study was performed to evaluate feasibility and reproducibility of two-dimensional shear wave elastography (2D SWE) for evaluation of tissue stiffness and to examine technical factors that affect shear wave speed (SWS) measurements in adult dogs. Nine healthy, 2 year-old, adult beagles with the median weight of 9.8 kg were included. In this prospective, experimental, exploratory study, 2D SWE (Aplio 600) from the liver, spleen, kidneys, pancreas, prostate, lymph nodes (submandibular, retropharyngeal, axillary, medial iliac, and inguinal), submandibular salivary gland, and thyroid was performed in anesthetized beagles. Color map was drawn and SWS of each SWE were measured as Young’s modulus (kPa) and shear wave velocity (m/s). The effect of measuring site, scan approach, depth, and anesthesia on SWE was assessed in abdominal organs by two observers independently. A total of 27 SWE examinations were performed in 12 organs by each observer. All SWS measurements were preformed successfully; however, SWE in the renal medulla could not be successfully conducted, and it was excluded from further analysis. Interobserver agreement of SWE was moderate to excellent in all organs, except for the left liver lobe at 10–15 mm depth with the intercostal scan. In the liver, there was no significant effect of the measuring site and scan approach on SWE. SWS of the liver and spleen tended to be higher with increasing the depth, but no significant difference. However, anesthesia significantly increased tissue stiffness in the spleen compared to awake dog regardless of the depth (P < 0.05). There was a significant difference in SWS according to the measuring site in the kidneys and pancreas (P < 0.001). 2D SWE was feasible and highly reproducible for the estimation of tissue stiffness in dogs. Measuring site and anesthesia are sources of variability affecting SWE in abdominal organs. Therefore, these factors should be considered during SWS measurement in 2D SWE. This study provides basic data for further studies on 2D SWE on pathological conditions that may increase tissue stiffness in dogs.

Comparison of Supersonic Shear Wave Imaging-Derived Renal Parenchyma Stiffness Between Diabetes Mellitus Patients With and Without Diabetic Kidney Disease

This study aims to evaluate the difference in renal parenchyma stiffness assessed by measuring Young's modulus (YM) using a supersonic shear wave imaging (SSI) technique among healthy patients and patients with type 2 diabetes mellitus (DM) with and without diabetic kidney disease (DKD). We analyzed the correlations of YM with clinical information and conventional ultrasound parameters. All patients (N = 124) were divided into three groups: (i) healthy patients (patients without kidney disease or type 2 DM, N = 31); (ii) patients with type 2 DM without kidney disease (N = 38); and (iii) patients with DKD (N = 55). Conventional and SSI ultrasound examinations were performed in all individuals for both kidneys. Then, we recorded renal length, width, parenchyma thickness, interlobar arterial resistive index (RI) and values of mean, mininum and maximum YM. The mean values of these parameters for the left and right kidneys were calculated for statistical analysis. Statistical significance was considered at p < 0.05. Among all ultrasound parameters, the mean YM demonstrated the largest area under the receiver operating characteristic (ROC) curve (0.860). The areas under the ROC curve (AUCs) for renal length, width, parenchyma thickness, interlobar arterial RI, minimum YM and maximum YM were 0.493, 0.616, 0.507, 0.733, 0.848 and 0.794, respectively. The corresponding cutoff value of mean YM was 31.73 kPa, with a sensitivity of 85.5% and a specificity of 71.0%. The mean YM in patients with type 2 DM without kidney disease (31.44 ± 3.83 kPa) was significantly higher than that in the healthy group (26.45 ± 4.32 kPa) and lower than that in the DKD group (37.60 ± 6.56 kPa). Patients with type 2 DM without kidney disease were considered as stage 0 of DKD. Thus, the mean YM in the control group was significantly lower than that in the stage 0, 2, 3, 4 and 5 subgroups. The mean YM in the stage 0-2 subgroups was lower than that in the stage 5 group, and the mean YM in the stage 0 group was lower than that in the stage 4 group. In the DKD group, the mean YM had a positive correlation with cystine-c (r = 0.634), urea (r = 0.596), creatine (r = 0.690), uric acid (r = 0.263), albumin/creatinine ratio (r = 0.428) and the presence or absence of diabetic retinopathy (r = 0.354). The mean YM also had a negative correlation with the estimated glomerular filtration rate (r = -0.657). SSI is a non-invasive method with which to diagnose DKD and has a performance superior to that of conventional ultrasound. In addition, SSI may provide a secondary index for the staging of DKD and the monitoring of renal damage in type 2 DM patients.

Utility of ultrasound elastography in postoperative follow-up of children with unilateral ureteropelvic junction obstruction

Introduction:

We aimed to determine whether shear wave velocity (SWV) on ultrasound elastography is useful in follow-up of children with ureteropelvic junction obstruction (UPJO) following pyeloplasty.

Methods:

Consecutive children with unilateral UPJO who were co-operative for elastography (n = 31) were included. SWV of normal kidney was used as control, and it was compared with that of the affected kidney (UPJO) in the same patient. They were followed up with elastography at 3 months and elastography + renogram at 6 months postoperatively. In patients with a static renogram at 6 months, the study was repeated at 1 year. Patient outcomes were classified as improved at 6 months, static at 6 months, and worsened at 1 year based on ultrasound and renogram findings. The SWV was compared between the different outcomes.

Results:

Thirty-one children with a median age of 8.5 years were studied (m:f = 29:2; L:R = 22:9). The mean SWV was significantly higher (3.21 m/s) in UPJO kidney compared to the SWV (2.72 m/s) found in normal kidney (P = 0.011). The mean SWV was significantly less at 3 months (2.73 m/s) and 6 months (2.57 m/s) postoperative follow-up (P = 0.018 and P= 0.001). Among the patients who improved, the mean SWV was 2.65 m/s. This SWV was significantly raised (3.57 m/s) in patients whose condition remained static (P = 0.006) and even higher (4.36 m/s) in those who worsened (P = 0.001).

Conclusions:

SWV was significantly higher in UPJO compared to normal kidneys in children. It is useful in assessing postoperative resolution, and a rising velocity can be useful as an early marker of recurrence in UPJO.

Magnetic resonance elastography vs. point shear wave ultrasound elastography for the assessment of renal allograft dysfunction

PURPOSE

To investigate the utility of magnetic resonance elastography (MRE) vs. ultrasound (US) point shear wave elastography (pSWE) for the assessment of chronic renal allograft dysfunction, prediction of outcome and determine the correlation with Banff pathology scores.

METHODS

In this IRB approved prospective study, 27 enrolled patients with functional (n = 15) and chronic dysfunctional (n = 12) renal allografts underwent same day 2D MRE and pSWE. Histogram parameters [including mean, median, standard deviation, kurtosis and skewness] of the magnitude of the complex shear modulus (MRE) and median Young's modulus (pSWE) were measured in the cortex (MRE and pSWE) and combined corticomedullary regions (MRE). Histopathology was available for 16 patients (4 functional, 12 dysfunctional).

RESULTS

MRE and pSWE stiffness were not significantly different between functional and dysfunctional groups (p range 0.139-0.347). The skewness of MRE corticomedullary stiffness was significantly lower (p = 0.04) in patients with chronic dysfunction and correlated significantly with Banff histopathologic scores (range r=-0.518-0.567, p = 0.035-0.040). MRE cortical and corticomedullary mean stiffness showed strong performance in predicting graft loss/relist (AUC 0.958, p = 0.011 for both). Reliable pSWE measurements were obtained in 13 patients (48 %). pSWE stiffness did not correlate with Banff scores and did not predict outcome.

CONCLUSIONS

The skewness of MRE corticomedullary stiffness is sensitive to changes in chronic allograft dysfunction, while mean/median MRE renal stiffness and median US stiffness did not differentiate patients with stable function vs those with chronic renal allograft dysfunction. MRE corticomedullary mean stiffness appears to be a predictor of graft loss/relist. pSWE was not found to be a useful method for assessing renal allografts.

Pre-procedural shear wave elastography on prediction of hemorrhage after percutaneous real-time ultrasound-guided renal biopsy

PURPOSE

To evaluate the relationship between renal elasticity which was determined with shear wave elastography (SWE) and hemorrhage in patients who undergone percutaneous renal parenchyma biopsy (PRB).

MATERIALS AND METHODS

In total, 60 patients who were performed ultrasound-guided PRB after the B-mode ultrasonography and SWE assessment were recruited in this study. All patients' serum creatinine, blood urea nitrogen and coagulation tests before PRB were obtained from medical records. The patients were divided into two groups who did and did not develop hemorrhage after PRB. We investigated whether there was any statistically significant difference between the two groups in terms of laboratory findings, B-mode ultrasonographic measurements and SWE measurements.

RESULTS

Of the 60 patients, 23 (38.3%) had post-procedure hemorrhage and 37 (61.7%) had not. Mean hemorrhage size was 17.04 mm (7-50 mm). The mean value of renal cortical shear wave velocity of all patients was 1.91 m/s (0.96-3.57 m/sn). Patients with post-procedure hemorrhage had significantly lower mean shear wave velocity compared with patients with no hemorrhage (p < 0.05). ROC curve analysis suggested that the optimum SWV cutoff point for hemorrhage presence was 1.21 m/sn, with 39.1% sensitivity and 97.3% specificity. There was no other statistically significant demographic, ultrasonographic or laboratory value differences between two groups.

CONCLUSION

Although shear wave velocities have low sensitivity for hemorrhage after renal biopsy, high specificity and statistically significant difference in hemorrhage and non-hemorrhage group suggest that patients who have lower renal cortical shear wave velocity have a tendency to hemorrhage after PRB.

Magnetization Transfer Imaging Is Unaffected by Decreases in Renal Perfusion in Swine

OBJECTIVES

Multiparametric renal magnetic resonance imaging (MRI), including diffusion-weighted imaging, magnetic resonance elastography, and magnetization transfer imaging (MTI), is valuable in the noninvasive assessment of renal fibrosis. However, hemodynamic changes in diseased kidneys may impede their ability to measure renal fibrosis. Because MTI assesses directly tissue content of macromolecules, we test the hypothesis that MTI would be insensitive to renal hemodynamic changes in swine kidneys with acute graded ischemia.

MATERIALS AND METHODS

Seven domestic pigs underwent placement of an inflatable silicone cuff around the right renal artery to induce graded renal ischemia. Multiparametric MRI was performed at baseline, 50%, 75%, and 100% renal artery stenosis as well as reperfusion. Measurements included regional perfusion, R2*, apparent diffusion coefficient (ADC), stiffness, and magnetization transfer ratio (MTR) using arterial spin-labeled MRI, blood oxygenation-dependent MRI, diffusion-weighted imaging, magnetic resonance elastography, and MTI, respectively. Histology was performed to rule out renal fibrosis.

RESULTS

During graded ischemia, decreases in renal perfusion were accompanied with elevated R2*, decreased ADC, and stiffness, whereas no statistically significant changes were observed in the MTR. No fibrosis was detected by histology. After release of the obstruction, renal perfusion showed only partial recovery, associated with return of kidney R2*, ADC, and stiffness to baseline levels, whereas cortical MTR decreased slightly.

CONCLUSIONS

Renal MTI is insensitive to decreases in renal perfusion and may offer reliable assessment of renal structural changes.

Evaluation of maternal renal cortical elasticity in pregnancies with early- and late-onset preeclampsia

Objective: The current study aimed to investigate renal cortical elasticity (RCE) in early- and late-onset preeclampsia patients and compare the results with healthy controls.Materials and methods: The study consisted of 136 pregnant women. Three groups were identified as; the late-onset preeclampsia (LOP) group (n = 40), the early-onset preeclampsia (EOP) group (n = 32) and the control group (n = 64). RCE values were measured by point shear wave elastography (pSWE). Nine measurements were taken for each kidney and the mean of nine measurements was accepted as the mean RCE value for each kidney. The arithmetic mean of left and right RCE values was accepted as the overall RCE value of a subject. Groups were compared in terms of clinical and biochemical parameters, ultrasonography findings and pSWE values.Results: There was a statistically significant difference between groups in terms of overall RCE values (F[2,133] = 17.96, p < .001). Post hoc comparisons indicated that both preeclampsia groups exhibited significantly higher RCE values than the control group. However, overall RCE values were not significantly different between the EOP and LOP groups. Overall RCE values were significantly and positively correlated with systolic blood pressure (r = 0.363, p < .001), diastolic blood pressure (r = 0.347, p < .001), proteinuria (r = 0.343, p < .001), serum creatinine level (r = 0.181, p = .035), serum uric acid level (r = 0.243, p = .004) and blood urea nitrogen (r = 0.27, p = .001).Conclusion: Our study demonstrated that maternal renal cortical stiffness increased in women with preeclampsia. The increased RCE values may be indicative for the severity of preeclampsia due to positive correlations between renal cortical stiffness and systolic - diastolic blood pressure and serum creatinine level.

Combined Acoustic Radiation Force Impulse and Conventional Ultrasound in the Quantitative Assessment of Immunoglobulin a Nephropathy

We investigated the value of combined acoustic radiation force impulse (ARFI) imaging and conventional ultrasound (US) in identifying renal histopathological fibrosis with immunoglobulin A nephropathy. A total of 146 patients with immunoglobulin A nephropathy, pathologically confirmed by renal biopsy were grouped according to Oxford classification and Katafuchi grading, were included in the test group, and 39 healthy volunteers were included in the control group. Receiver operating characteristic (ROC) curves were constructed to compare the diagnostic accuracy of ARFI, renal lengths, parenchymal thicknesses and interlobular arterial resistance index (RI) and their combinations in identifying Katafuchi grading at renal biopsy. Shear wave velocity (SWV), renal length, renal parenchyma thickness and the interlobular arterial RI were correlated with Katafuchi grading, mesangial hypercellularity (M) and tubular atrophy/interstitial fibrosis (T) (r = -0.504 to -0.407, p < 0.01) but were not correlated with endocapillary hypercellularity (E) or segmental glomerulosclerosis (S). The area under the curves of SWV value + conventional US index (renal length, renal parenchyma thickness and interlobular arterial RI) was higher than those of the SWV value or of the conventional US index alone. The combination of ARFI imaging and conventional US can improve the diagnostic performance in quantitative evaluation pathologic damage in patients with immunoglobulin A nephropathy.